The production of Anopheles mosquitoes from their aquatic, larval habitats is the primary determinant of their density in malaria endemic areas. In nature, microorganisms form an essential component of the natural diet of larval mosquitoes; our work under the Parent Grant to this FIRCA application indicates that variation in quantity and quality of microorganisms results in variable larval growth, and therefore adult productivity. We argue that the significance of microorganisms to larval mosquitoes creates a weak link in their biology that can potentially be exploited to manage mosquito populations. By understanding how microorganisms supply nutrients to larval mosquitoes, sustain and limit larval mosquito growth, are naturally pathogenic to larvae, or can be engineered to be pathogenic, we can identify biological factors in larval habitats that may be amenable to manipulation. In this proposal, we will quantify the nutrient regime, characterize the microbial community, and link microbial production to adult mosquito production in larval habitats of the mosquito Anopheles gambiae s.1. in the Asembo Bay study area in western Kenya. The Kenyan collaborator for this application, Dr. John M. Vulule, has ongoing studies of the distribution and chemical composition of these habitats in a 120 km2 zone of this study area, and has found 1,766 habitats clustered into 57 areas. We hypothesize that these habitats are nutrient poor, and show both algal autotrophic productivity and bacterial heterotrophic productivity; the former is likely to weigh more significantly to mosquito growth. Methods include sampling habitat water and quantifying inorganic and organic nutrient regimes; characterization of the microbial community using direct count and bacterial isolation and identification; and quantitative larval growth studies linked to estimations of algal and bacterial productivity.